Filter device

ABSTRACT

The invention relates to a filter device comprising a pot-shaped filter housing ( 1 ) that defines a longitudinal axis along which a filter element ( 13 ) can be inserted into and removed from the filter housing ( 1 ). A retaining device detachably retains the filter element ( 13 ) in the filter housing ( 1 ) and comprises first and second retaining elements that are provided on the inner side of the filter housing ( 1 ) and on the filter element ( 13 ) and that interact with one another. At least one set of the retaining elements has a shape coaxial to the longitudinal axis of the filter housing ( 1 ) and forms at least a part of a thread in such a manner that, when the filter element ( 13 ) is rotated about its longitudinal axis, it is locked in a form-fit.

[0001] The invention relates to a filter device with a cup-shaped filter housing which defines a longitudinal axis, along which a filter element can be inserted into the filter housing and can be removed from it, and with a retaining means which is used for detachable fixing of the filter element in the filter housing and which has first and second retaining elements which interact with one another and which are provided on the inside of the filter housing and on the filter element.

[0002] Filter devices of this type are known. A not insignificant portion of production costs arise in these filter devices for the execution of the retaining means for detachable fixing of the filter element. In the filter device of the above-mentioned type addressed in EP 0 891 214 B1 the retaining means has a spring arrangement of two compression springs which work against one another, by the resulting spring force of which an end piece which is located on the filter element and which acts as a sealing and retaining element is slipped onto the housing-side retaining element which is formed by the connecting piece which extends into the support tube of the filter element on the head of the filter housing.

[0003] The comparatively complex construction of the retaining means leads to high production costs, On the basis of this state of the art, the object of the invention is therefore to devise a filter device of the type under consideration which is characterized by simple construction of the retaining means for the filter element and by the corresponding low production costs,

[0004] In a filter device of the above-mentioned type this object is achieved as claimed in the invention in that at least one of the retaining elements has a shape which forms at least part of a thread and which is concentric to the longitudinal axis of the filter housing so that the filter element after turning around its longitudinal axis is fixed by an interlocking connection.

[0005] A retaining means which acts in the manner of a screwed connection and in which the filter element is fixed interlocked by turning can be implemented with simple structural means so that in the desired manner economical production is possible. Since by turning the filter element an interlocked connection between the filter element and the filter housing is produced, the additional advantages of ease of operation and high operating reliability are achieved.

[0006] Preferably the arrangement is made such that the first retaining elements form a guide for the second retaining elements when the filter element is rotated and the guide has a thread pitch which is referenced to the longitudinal axis on at least part of its length.

[0007] The second retaining elements can be cams which project transversely to the longitudinal axis of the filter housing and are guided in cam paths which form the first retaining elements and have a thread pitch on at least part of their path length. This allows the possibility of prompt fixing in a simple manner and the connection can be made self-locking by way of the thread pitch. While maintaining the advantages of an otherwise conventional screw connection in this area, the indicated connection can be produced and broken again within a short time with little expenditure of force. In addition, the alignment of the connection is largely unambiguous, i.e., the installation situation of the interchangeable filter element relative to the filter housing can be easily reproduced.

[0008] Preferably there are cams on the inside of the filter housing and there are cam paths on the filter element.

[0009] If the filter element is a filter cartridge which has a fluid-permeable support tube which is surrounded by filter material and an end cap which borders the edge of the filter material and which is located on its bottom-side end assigned to the bottom of the cup-shaped filter housing, the cam paths can be made peripheral on it.

[0010] In these embodiments the production of the filter device is especially simple and economical if the cams are made on the inside of a ring body which is mounted in the cup-shaped filter housing in its bottom area.

[0011] The invention is described below in detail with reference to an embodiment as illustrated in the drawings.

[0012]FIG. 1 shows a lengthwise section of one embodiment of the filter device with a filter cartridge located in the filter housing, which section is shown schematically simplified;

[0013]FIG. 2 shows a perspective lengthwise section of only the cup-shaped part of the filter housing of the embodiment without the housing cover, only one bottom-side end cap of the filter cartridge which is not otherwise shown being fixed by interlocking in the filter housing;

[0014]FIG. 3 shows a perspective view of the end cap of the filter cartridge drawn on a larger scale compared to FIGS. 1 and 2, and

[0015]FIG. 4 shows an overhead view of a ring body which is attached in the bottom-side end area of the filter housing of the embodiment with cams which are used as retaining elements and which project inwardly.

[0016] As shown in FIGS. 1 and 2, the illustrated and described embodiment of the filter device has a filter housing 1 in the form of a cup which is rotationally-symmetrical in its outline to the longitudinal axis 3 and which has a closed bottom 5 and a housing cover 7 which seals the opposing top end and which is shown only in FIG. 1. The housing cover 7 has on a sleeve-shaped projection 9 an outside thread which can be screwed to the inside thread 11 on the top end of the cup-shaped part of the filter housing 1. Sealing elements for sealing between the housing cover 7 and the cup-shaped part of the filter housing 1 are not shown in the schematic from FIG. 1.

[0017] A filter cartridge 13 which is concentric to the longitudinal axis 3 can be held in the filter housing 1 and conventionally said filter cartridge has an inner, fluid-permeable support tube 15 which is surrounded by filter material 17. On the bottom-side end facing the bottom 5 of the filter housing 1 the filter cartridge 13 is closed by an end cap 19 which forms a border for the facing lower end edge area of the filter material 17. For this purpose the end cap 19 has a central, circular cylindrical journal 21 which extends into the interior of the support tube 15 of the filter cartridge 13 and on its end edge has a slight bevel 22 (FIG. 3). Between the outside of the journal 21 and the radially outer peripheral jacket 23 of the end cap there is an annular groove-like recess 25 into which the lower edge of the filter material 17 fits.

[0018] The filter cartridge 13 on the opposing top end has a top head cap 27 which borders the filter material 17 and the edge of the support tube 15 and which forms a connecting sleeve 29. When the housing cover 7 is screwed onto the cup-shaped part of the filter housing 1 a connecting piece 31 which forms an outlet for the filtered fluid engages the connecting sleeve 29 in order to produce the fluid connection to the interior of the support tube 15, an O ring 33 on the connecting sleeve 29 sealing the interior of the filter cartridge (the clean side of the filter device) against the space of the filter housing 1 surrounding the filter cartridge 13 (the fouled side of the filter device). The inlet for the fluid which is to be filtered into the filter housing 1 is not shown in the figures.

[0019] The configuration of the retaining means for detachably fixing the filter cartridge 13 in the filter housing 1 is especially apparent from FIGS. 2 to 4. The retaining means has first retaining elements which are associated with the filter cartridge 13 and second retaining element which are associated with the filter housing 1. The retaining elements which are associated with the filter cartridge 13 are located on the end cap 19. The retaining elements which are associated with the housing 1 are located on a ring body 35 which is mounted in the filter housing 1 in the vicinity of its bottom 5 and which is shown separately in FIG. 4. As is apparent from this figure, the ring body 35 on its inner jacket surface has four journal-like cams 37 which project radially to the inside and which are arranged offset to one another by 90°. On the end edge facing the bottom 5 of the filter housing 1 the ring body 35 on the peripheral side has a slight rounding 39 with which the ring body 35 is matched to the slight arch of the inside wall of the filter housing 1 in the bottom area. As already indicated, the ring body 35 in the filter housing 1 is attached by pressing or welding in.

[0020] The radially projecting cams 37 of the ring body 35 are designed to engage the cam paths 41 (see FIG. 3) which are made as the retaining elements belonging to the filter cartridge 13 on their end cap on the outer peripheral side. These cam paths 41 are formed by recesses which are machined into the periphery of the jacket 23, as the guide for each cam 37 there being one cam path 41 each so that there are four cam paths 41. Each of these cam paths 41 forms a groove which is open on the lower end edge of the jacket 23 of the end cap 19, these open areas 43 of the grooves being offset by 90° each to one another, so that when the filter cartridge 13 is inserted into the filter housing 1 the cams 37 which are mounted on the housing side can move into the open areas 43. These open areas 43 adjoin areas 45 with a thread-like pitch for each cam path 43. If the filter cartridge 13 is turned around the longitudinal axis 3 after the cams 37 move into the open areas 43 of the cam paths 41, the cams 37 run over the pitch areas 45, i.e., the cam ramps which are formed thereby, whereby a holding force which acts in the axial direction is produced on the end cap 19 of the filter cartridge 13, by interlocking engagement between the cams 37 and the cam paths 41. The locking of the filter cartridge 13 which is created in this way by turning around the longitudinal axis 3 in one direction of rotation can be easily released by turning the filter cartridge 13 in the opposite direction of rotation in order to remove it again from the filter housing 1. As is best illustrated in FIG. 3, the cam paths 41 following their starting area 45 which has the pitch transition into a groove which extends along the entire periphery of the jacket 23 of the end cap 19. The end cap 19 in the illustrated and described embodiment can be advantageously press-formed from a plastic material. The edge of the filter material 17 held in the recess 25 within the jacket 23 of the end cap 19 can be cemented to the end cap 19. The journal 21 of the end cap projecting into the interior of the support tube 15 of the filter cartridge 13 can likewise be cemented to the support tube 15.

[0021] It goes without saying that instead of using four cams 37 and four associated cam paths 41 there can be a different number of cams and cam paths, preferably there being no fewer than three cams and cam paths. Instead of the configuration shown in which for the cam paths 41 the ramp-like area 45 which has the pitch adjoins an area without a pitch, there can be cam paths 41 with a continuous pitch. Instead of the configuration of the retaining elements shown in the illustrated embodiment as individual cams 37, there could be a threaded connection between the end cap 19 and the filter housing 1 by means of continuous thread elements in the manner of a screw connection with an inside thread and/or outside thread elements which are made peripherally continuous. 

1. A filter device with a cup-shaped filter housing (1) which defines a longitudinal axis (3), along which a filter element (13) can be inserted into the filter housing (1) and can be removed from it, and with a retaining means which is used for detachable fixing of the filter element (13) in the filter housing (1) and which has first and second retaining elements (41 and 37) which interact with one another and which are provided on the inside of the filter housing (1) and on the filter element (13), characterized in that at least one set (41) of the retaining elements has a shape which forms at least part of a thread and which is concentric to the longitudinal axis (3) of the filter housing (1) so that the filter element (13) after turning around its longitudinal axis (3) is fixed by an interlocking connection.
 2. The filter device as claimed in claim 1, wherein the first retaining elements (41) form a guide for the second retaining elements (37) when the filter element (13) is rotated and the guide has a thread pitch relative to the longitudinal axis (3) on at least part (45) of its length.
 3. The filter device as claimed in claim 2, wherein the second retaining elements are a plurality of cams (37) which project transversely to the longitudinal axis (3) of the filter housing (1) and wherein the first retaining elements which have a thread pitch are cam paths (41, 45) into which the cams (37) can move when the filter element (13) is inserted into the filter housing (1).
 4. The filter device as claimed in claim 3, wherein there are cams (37) on the inside of the filter housing (1) and there are cam paths (41, 45) on the filter element (13).
 5. The filter device as claimed in claim 4, wherein the filter element is a filter cartridge (13) which has a fluid-permeable support tube (15) which is surrounded by filter material (17) and an end cap (19) which encompasses the edge of the filter material (17) and which is located on its bottom-side end which is assigned to the bottom (5) of the cup-shaped filter housing (1), and the cam paths (41, 45) are made peripherally on the end cap.
 6. The filter device as claimed in claim 5, wherein on the inside wall of the filter housing (1) there are journal-like cams (37) which project radially to the inside, which are offset to one another by a definable angle, and which lie on the inside wall of the filter housing (1) in a common plane for interaction with the cam paths (41, 45) which are made correspondingly on the end cap (19) of the filter element (13).
 7. The filter device as claimed in claim 6, wherein there are four projecting cams (37) on the inside wall of the filter housing (1) offset by 90° to one another and they interact with four correspondingly arranged cam paths (41,45).
 8. The filter device as claimed in claim 6 or 7, wherein the cam paths (41, 45) on the end cap (19) are formed by grooves which run in areas (45) with a thread-like pitch and which on the peripheral areas (43) of the end cap (19) which are offset to one another by one definable angle each are open on the lower end edge of the end cap (19) so that the cams (37) can be moved into the grooves when the filter element (13) is inserted into the filter housing (1).
 9. The filter device as claimed in claim 8, wherein the grooves are arranged offset to one another by 90° each on the four peripheral areas (43) of the end cap (19).
 10. The filter device as claimed in one of claims 4 to 9, wherein the cams (37) are formed on the inside of a ring body (35) which is mounted in the cup-shaped filter housing (1) in its bottom area. 